Electron tube



E. A. FRITZ ELECTRQN TUBE Aug. 18, 1936.

Filed March 16, 1931 Patented Aug. 18, 1936 assign ran an answer Emerson "roan Earl A. Frita, Milwaukee. Wis., assignor to @ut= ler-iilammer, Zinc, Milwaukee, Wis., a cargo ration of Delaware Application March 16, 1931, Serial No. 5232,99?

a Claim.

This invention relates to improvements in gaseous electron discharge devices which are equipped with a grid for the control of the discharge current between the main electrodes and has among its objects to provide for a more emcient control of the operation of such a tube by means of the grid.

Another object is to provide for a grid of large heat radiating capacity, the effectiveness of which is not impaired by the heating thereof due to the heat radiated by the cathode and by the discharge upon the passage of relatively high currents.

Another object is to provide a grid, the effectiveness of which is not impaired to the degree customary with other known forms by the deposition of emission increasing substance which is thrown off by the emitting cathode.

I Another object is to provide a grid which will reduce the heat radiation losses of the cathode.

Another object is to provide a grid which will shield the walls of the tube against the direct impact of the electrons emitted by the cathode and thus prevent the accumulation of a charge on said walls which interferes with the efiective control of the discharge by the grid.

Other objects and advantages will appear from the following specification of the invention.

The drawing illustrates one embodiment of the invention.

In the drawing- Figure 1 is a longitudinal section of a tube along lines A--A of Fig. 2, while l 'igzisacrossseetionalong linesB-Bef Fig. l.

Referring to the drawing, an electron tube of the vapor or gaseous type which may contain for instance mercury vapor has a filamentary cathode l which, in the present instance, is illustrated as a spiral conductor. A conventional anode 2 is mounted concentric with and at one end of the longitudinal axis of the cathode l. The cathode is surrounded by a concentric cylindrical grid 3, the sides of which are solid. The cylinder is closed at its lower end by a head 6, the only openings of which are those permitting the passage of the terminal wires for the cathode, while the upper end 5 which is interposed between the cathode l and the anode 2 is also a solid sheet provided only with one or several openings 6 of a minimum cross section just sufilcient to permit the passage of the discharge current between cathode and anode without unduly restricting the path thereof and so located that substantially no electrons from the cathode can reach the walls of the container.

The cathode i is frequently coated with an emission increasing substance such as metal oxides and such material is gradually dispersed by the impact of positive ions on the surface of the cathode. Such substance is then disposed on the surface of the grid adjacent to the cathode. In the prior art tubes, wherein the grid consisted of a series of threads or a mesh or sheet with many perforations, some of the emitting substance was also deposited on the outer surfaces of the grid, and after the lattter was heated up due to prolonged operation of the tube, the so deposited emission increasing substance caused secondary emission from the grid, producing disturblng ionization, which resulted in decreasing the effectiveness of the grid upon the main discharge and the ultimate failure of the grid to function.

With my improved grid, any emission increasing substance which may be thrown off the cathode is deposited on the inside surfaces of the grid and thus is incapable of providing electrons through secondary emission, to produce the disturbing ionization outside of the latter, so that the effectiveness of the grid is maintained throughout the life of the tube.

By arranging the openings which are necessary to permit passage of discharge from the cathode to the anode on the side opposite the anode, I obtain an effective shielding of the walls of the tube against the impact of electrons thrown oif bythe cathode, while the balance of the wall of the tube is completely shielded by the grid itself. Hence the electrons emitted from the cathode form beams which are limited in their spread by the openings and w ch terminate at the anode, while practically no electrons strike the wall of the tube.

In making the walls of the grid substantially solid, its outer radiating surface is greatly increased, thus aifording great heat dissipating capacity which reduces the heating of the grid, while at the same time the cathode is heat shielded, which reduces its heat radiation and correspondingly reduces the amount of energy required to heat it to the proper operating temperature.

What I claim as new and desire to secure by Letters Patent is:

1. In a gaseous electron discharge tube, in combination, a heated cathode, an anode and a control grid which consists of a solid sheet, com- 55 pletely enclosing the cathode, except for an area so located with respect to the cathode and anode as to concentrate the electron stream passing said area into beams terminating at the anode, said grid being provided with a separate terminal.

2. In a gaseous electron discharge tube, in combination, a heated cathode, an anode and a control grid which completely surrounds the cathode in the form of an enclosure, imperiorate, except for apertures so located that all straight lines drawn from the cathode and passing therethrough terminate at the anode, said grid being provided with a separate terminal.

3. In a gaseous electron discharge tube, in combination, a heated cathode, an anode and a control grid, said grid completely enclosing said cathode except for apertures so located as to prevent disturbing ionization efiects by limiting the path of secondary electrons to the space inciosed by it, said grid being provided with a separate terminal.

4. In a gaseous electron discharge tube, in com bination, a heated cathode, an anode and a control grid, said grid completely enclosing the oathode in the form of a heat shield except for opencontrol electrode encompassing said cathode comprising an imperforate hollow body portion and two end portions, one of said end portions having an aperture therein to allow passage of said leading-in wires and the other of said end 5 portions being disposed between said anode and cathode and having apertures therein through which the discharge between said cathode and anode occurs, the total eifective area of the apertures of said second end portion with respect to the cathode being greater than the eiiective area of the aperture in said first end portion.

6. A gaseous discharge device comprising an enclosing vessel having a stem, an incandescible cathode, leading-in wires for said cathode embedded in .said stem, an anode adjacent said cathode, and a control electrode encompassing said cathode comprising an imperforate hollow body portion and two end portions, one of said end portions being disposed between said cathode and anode and being apertured for passage therethrough of the discharge from said cathode to said anode and the other of said end portions being apertured for passage therethrough of said leading-in wires and having .less open aperture area than the former end portion, said control electrode confining passage of the discharge between said cathode and anode to the aperture area of the end portion disposed between said cathode and anode.

- EARL A. FRITZ. 

